JP3674401B2 - Heat exchanger tube for heat exchange - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to heat exchange in a heat recovery / use system that recovers heat energy from high-temperature combustion exhaust gas of municipal waste, coal, sewage treatment, paper sludge, and other industrial wastes through a fluid such as steam or air to generate power. It relates to electric heating tubes.
[0002]
[Prior art]
Exhaust gas generated when incinerating municipal waste and industrial waste is composed of NaCl, KCl and Na containing hydrogen chloride gas, sodium, potassium, etc.₂SO_FourContains other basic salts. The corrosivity of hydrogen chloride and basic salts increases as the temperature increases. Therefore, in a waste heat boiler that recovers heat from the combustion exhaust gas of municipal waste and industrial waste, the steam flowing in the heat exchange tube is generally used to reduce the damage caused by corrosion caused by hydrogen chloride and basic salts. It is suppressed to 300 ° C. or lower.
[0003]
Therefore, in order to recover higher-temperature heat energy from this corrosive environment, as disclosed in Japanese Patent Laid-Open No. 10-274401, the outer surface of a boiler tube made of a heat-resistant metal is sprayed or physically vapor-deposited. Alternatively, a method has been devised in which the high temperature corrosion resistance of the heat exchange tube is improved by coating with a ceramic film by chemical vapor deposition. Since the boiler tube is based on metal, it has the toughness necessary for a heat exchange tube, and its surface generally has excellent high-temperature strength and low wettability with salts, and exhibits excellent high-temperature corrosion performance. To secure a high degree of corrosion resistance in high-temperature exhaust gas.
[0004]
[Problems to be solved by the invention]
However, in the conventional heat exchange tube as described above, ceramics and metal are bonded by thermal spraying or vapor deposition, so if exposed to high temperature corrosive atmosphere for a long time, the difference in thermal expansion coefficient between ceramic and metal Due to the influence of the ceramic, the ceramic is easily peeled from the metal surface. And the metal part from which the ceramic peeled begins to corrode. Therefore, this method has a problem that it is insufficient as a method for reliably preventing corrosion of the heat exchange tube.
[0005]
Therefore, the present invention has been made to solve the problem of peeling of ceramics and metal due to a difference in thermal expansion without reducing the thermal conductivity, and the metal surface is corroded even when exposed to a high temperature corrosive atmosphere for a long time. Therefore, an object of the present invention is to obtain a heat exchanger tube for heat exchange that can recover heat at a higher temperature than the conventional one.
[0006]
[Means for Solving the Problems]
  The heat transfer heat transfer tube according to the present invention is provided in a high-temperature gas atmosphere, and the heat-exchange heat transfer tube for exchanging heat from the high-temperature gas to the heated fluid in the heat-transfer tube is a heat-resistant alloy. And the outer surface of the heat-resistant alloy tube is covered with a cover material made of a ceramic alloy composite material via a thermal expansion buffer material, and the thermal expansion buffer material is made of the cover material made of the ceramic alloy composite material and / or the heat-resistant alloy. The heat resistant alloy tube and at least a part of the thermal expansion buffer material are in contact with each other, and further, the thermal expansion buffer material and at least a part of the ceramic alloy composite material cover material are in contact with each other. From the layer structureThe ceramic alloy composite material constituting the cover material contains Al and AlN, and AlN is 1 wt % Or more 90 wt % Or less, the total ratio of (A1 + AlN + AlON) is 50 wt % Or more 100 wt % Or less(Claim 1).
[0007]
With this configuration, the heat-resistant alloy tube and the cover material made of the ceramic alloy composite material are exposed to a high-temperature atmosphere field and are not bonded even if they are thermally expanded in the tube axis direction. The cover material made of the ceramic alloy composite material is not damaged by the mutual shearing force. Even if the heat-resistant alloy tube expands in the radial direction, the expansion in the radial direction is absorbed by the thermal expansion buffer material of the intermediate layer, and the cover material made of the ceramic alloy composite material is not damaged. In addition, the thermal expansion buffer material and ceramic alloy composite cover material, or the thermal expansion buffer material and the heat-resistant alloy tube are in contact with each other but are not bonded. It has a strong structure against thermal shock related to Therefore, with this three-layer structure, the heat energy of the high-temperature fluid existing outside the cover material made of the ceramic alloy composite material can be stably transferred to the heated fluid flowing inside the heat-resistant alloy tube for a long time. .
[0008]
Regarding the heat transfer coefficient, the structure of the present invention has a three-layer structure in which at least a part of the heat-resistant alloy tube and the thermal expansion buffer material are in contact with each other, and at least a part of the thermal expansion buffer material and the cover material made of the ceramic alloy composite material are in contact with each other. Due to the structure, the thermal conductivity between the cover material made of the ceramic alloy composite material and the heat-resistant alloy tube is prevented from decreasing. If almost the entire inner surface of the cover material made of a ceramic alloy composite material and almost the entire outer surface of the heat-resistant alloy tube come into contact with the thermal expansion buffer material that is an intermediate layer, it is more effective in improving the thermal conductivity. preferable. If there is no thermal expansion cushioning material and the ceramic alloy composite cover material and the heat-resistant alloy tube are completely separated without contact, that is, if there is a gap, a gas insulation layer is formed there. This is not preferable because the thermal conductivity decreases rapidly.
[0009]
Here, the heat-resistant alloy that is the material of the tube through which the fluid to be heated flows is, for example, carbon steel / alloy steel for boilers, stainless steel, heat-resistant steel, Ni-based / Co-based heat resistant alloys (Inconel, Hastelloy, Stellite, etc. In addition, chromium, which is a refractory metal, is also suitable. Furthermore, the ceramic alloy composite material constituting the cover material can be selected from a wide range of oxides, carbides, nitrides, borides, silicides, carbons, and the like and mixtures thereof. As an example, Al as the oxide₂O_ThreeAnd Sialon (SiAlNO), SiC and B as carbide_FourC, nitride as AlN, Si_ThreeN_Four, TiB as boride₂As the silicide, MoSi or the like is suitable.
[0010]
In addition, the thermal expansion buffer material in the present invention is made of a material such as fiber, powder, film, tape, or the like mainly containing boron, carbon, or aluminum, and the outer surface of the heat-resistant alloy tube or the ceramic alloy composite. It consists of the thermal expansion absorption layer which has the space | gap formed in the inner surface of material-made cover materials, It is characterized by the above-mentioned (Claim 2).
[0011]
With this configuration, the volume ratio of the voids of the absorption layer changes with respect to the thermal expansion in the tube axis direction and the radial direction of the heat resistant alloy tube, so that the thermal expansion buffer material is made of the heat resistant alloy tube and the ceramic alloy composite cover material. The thermal expansion difference is absorbed, and damage to the ceramic alloy composite material cover material due to thermal shock can be prevented. The thermal expansion absorbing layer having voids may be formed on either the outer surface of the heat-resistant alloy tube or the inner surface of the ceramic alloy composite material cover material. Such a thermal expansion absorption layer can be formed by using materials such as fibers, powders, films, and tapes mainly composed of boron, carbon, or aluminum.
[0012]
  Further, the ceramic alloy composite material constituting the cover material in the present invention contains Al and AlN, wherein AlN is 1 wt% or more and 90 wt% or less, and the total ratio of (Al + AlN + AlON) is 50 wt% or more and 100 wt% or less. (Claims1).
[0013]
AlN, which is aluminum nitride, is a material with excellent corrosion resistance against air oxidation and various molten metals such as molten steel among ceramic materials. In an inert atmosphere, it is also excellent in corrosion resistance against various molten slag such as blast furnace slag. . In addition, since it has a relatively high hardness, it also has excellent wear resistance. Furthermore, since it has an extremely high thermal conductivity, a low thermal expansion coefficient, and a relatively low elastic modulus, it also has a relatively strong characteristic against thermal shock. Thus, AlN is a material having both excellent corrosion resistance and wear resistance, and relatively excellent thermal shock resistance.
[0014]
In addition to AlN, Al, which is metallic aluminum, is a material with extremely good thermal conductivity, is a metal advantageous for mitigating thermal shock, and is suitable as a constituent element of a heat transfer tube. In the process of manufacturing a ceramic alloy composite cover material, most of Al is N in the atmosphere.₂It changes to AlN by reacting with, and becomes a structure in which unreacted Al is dispersed in AlN, and AlN strengthens the bonding force between the particles.
[0015]
With this configuration, even if the sintered body is subjected to a thermal shock, AlN has a function of preventing shape deformation and Al surrounded by AlN mitigating the thermal shock. Therefore, in order to maintain this function, AlN must be contained at least 1 wt% or more. If the AlN content is less than 1 wt%, the bonding force between the particles is small and insufficient, and if it exceeds 90 wt%, the characteristics of the ceramic alloy composite material are close to ceramics and become brittle. Therefore, the content weight ratio of AlN is 1 wt% or more and 90 wt% or less.
[0016]
In the ceramic alloy composite material, Al and AlON are dispersed in AlN. When the content weight ratio of (Al + AlN + AlON) is 50 wt% or more and 100 wt% or less, the ceramic alloy composite material cover material can maintain high thermal shock properties while having thermal deformation characteristics. In addition, since nitride containing aluminum has poor wettability to oxide dust contained in high-temperature exhaust gas, it is difficult for dust to adhere to the cover material made of the ceramic alloy composite material if it contains a considerable amount of concentration. It has the characteristic of becoming. Therefore, if the content weight ratio of (Al + AlN + AlON) is 50 wt% or more, the property of preventing dust adhesion can be effectively exhibited. Further, AlON may be eliminated in the manufacture of the heat transfer tube, and the weight ratio of Al and AlN alone may be 50 wt% or more and 100 wt% or less.
[0017]
Here, AlON is a general term for solid liquids of Al, O, and N. As an example, AlON₁₁O₁₅N, AlON, Al₁₉₈O₂₈₈N_Four, Al₂₇O₃₉N, Al_TenN₈O_Three, Al₉O_ThreeN₇, SiAl₇O₂N₇, Si_ThreeAl_ThreeO_4.5N_FiveIs mentioned.
[0018]
  In the present invention, a release agent comprising a compound containing boron or carbon is applied to the outer surface of the heat-resistant alloy tube.3).
[0019]
By applying the release agent, the sliding between the heat-resistant alloy tube and the ceramic alloy composite material is improved, and the elongation due to the difference in thermal expansion between both members becomes smoother.
[0020]
  Furthermore, in the present invention, the ceramic alloy composite material has a porosity of 2% to 60% (claims).4).
[0021]
In manufacturing the cover material made of the ceramic alloy composite material, in order to reduce the porosity to less than 2%, a high temperature and high pressure atmosphere is required in the manufacturing process, and the manufacturing cost increases rapidly. The pores in the ceramic alloy composite material have a distorted shape rather than a simple circular hole. Its size is on the order of submicron or less to a few hundred microns in the distance between lines.
In such a ceramic alloy composite material having pores, when the porosity is larger than 60%, dust containing a basic salt easily penetrates into the ceramic alloy composite material, and the corrosion effect extends to the heat-resistant alloy tube. Therefore, the lower limit of the porosity is preferably 2%, and the upper limit is preferably 60%.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cross section of a heat exchanger tube for heat exchange according to an embodiment of the present invention (partially enlarged sectional view is also shown). The outside of the tubular body 1 made of a heat-resistant alloy is covered with a cover material 3 made of a ceramic alloy composite material via a thermal expansion buffer material 2, and a three-layer structure is formed by these three members 1, 2, and 3, and the thermal expansion buffer is made. The material 2 has a non-adhesive structure with respect to the cover material 3 and / or the heat-resistant alloy tube 1 made of a ceramic alloy composite material.
[0023]
High-temperature gas flows outside the outer surface of the cover material 3 made of the ceramic alloy composite material, and the heated fluid passes inside the heat-resistant alloy tube 1. The temperature of the high-temperature gas is 400 ° C. to 1200 ° C., and the ceramic alloy composite material constituting the cover material 3 is selected depending on the gas atmosphere conditions.
[0024]
The high temperature exhaust gas contains HCl and / or SOx. When a high-temperature dust collector having an exhaust gas temperature of 300 ° C. or higher is installed in the exhaust gas treatment line, the heat transfer heat transfer tube of the present invention can also be used for high-temperature exhaust gas after dust removal. The heated fluid flowing in the heat transfer heat transfer tube of the present invention is air, water vapor, CO₂Represents 2 to 25 vol% (wet base) of combustion exhaust gas, and according to the present invention, air and the combustion exhaust gas can be heated up to 800 ° C., and water vapor can be heated up to about 550 ° C. It was also confirmed that the heated fluid can be pressurized up to 100ata. The thickness of the heat-resistant alloy tube 1 is preferably 3 to 10 mm, the thickness of the thermal expansion buffer material 2 is preferably 0.1 to 8 mm, and the thickness of the ceramic alloy composite material cover material 3 is preferably 3 to 20 mm. If the thicknesses of the heat-resistant alloy tube 1, the thermal expansion buffer material 2, and the ceramic alloy composite material cover material 3 are made larger than the upper limit values, respectively, a heat transfer coefficient that is practically meaningful as a heat exchanger cannot be obtained. Moreover, if it makes smaller than each lower limit, it will become unable to endure a thermal shock as a heat exchanger tube, and will become easy to break.
[0025]
As shown in FIG. 1, the cover material 3 made of a ceramic alloy composite material covers the outside of the heat-resistant alloy tube 1 wrapped in the thermal expansion buffer material 2, and between the cover material 3 made of the ceramic alloy composite material and the heat-resistant alloy tube 1. Has a structure in which the thermal expansion buffer material 2 is interposed. The heat transfer heat transfer tube of the present invention does not use a method of adhering ceramics or corrosion resistant alloy to the outer surface of the heat resistant alloy tube 1 by thermal spraying, vapor deposition or other methods, and the cover material 3 made of a ceramic alloy composite material as a sleeve. Since it has a covered shape, even if the heat-resistant alloy tube 1 is exposed to a high temperature and expands in the tube axis direction and the radial direction, they are absorbed by the thermal expansion buffer material 2 and the cover material 3 made of a ceramic alloy composite material It has a structure that will not be damaged.
The cover material 3 made of the ceramic alloy composite material and the heat-resistant alloy tube 1 do not need to be perfect circles, and may be eccentric circles, ellipses, squares, or irregular shapes. Further, the heat-resistant alloy tube 1 and the ceramic alloy composite material cover material 3 do not have to be concentric. Further, the outer surface roughness of the heat-resistant alloy tube 1 may be rough or smooth.
[0026]
The outer surface of the heat-resistant alloy tube 1 and the inner surface of the thermal expansion buffer material 2, and the inner surface of the ceramic alloy composite material cover material 3 and the outer surface of the thermal expansion buffer material 2 flow outside as the contact area increases. Heat transfer from the high-temperature exhaust gas to the heated fluid in the heat-resistant alloy tube 1 is increased.
[0027]
  The thermal expansion buffer material 2 is made of a material mainly composed of boron, carbon, or aluminum. Using these materials, a thermal expansion absorption layer having voids is formed on the outer surface of the heat-resistant alloy tube 1 or the inner surface of the cover material 3 made of the ceramic alloy composite material. As a material for forming the thermal expansion absorption layer, for example, carbon fiber, boron, a film containing carbon, or aluminum foil is preferable. In addition, a plastic fine powder is sprayed on the heat-resistant alloy tube 1, or a tape containing carbon is wound around the heat-resistant alloy tube 1 to reduce the components from those components in the heat process for producing the heat transfer tube of the present invention. The boiling point medium may be volatilized, and the carbon-based material may be functionally used as a thermal expansion buffer material. Thermal expansion buffer material 2 is a heat-resistant alloy tube 1 and a cover material made of a ceramic alloy composite material.3Is used to absorb the difference in thermal expansion between the thermal expansion cushioning material 2 and the thermal expansion cushioning material 2 has a void, and fulfills this function by changing its volume ratio.
[0028]
Among the ceramic alloy composite materials, a material composed of AIN + Al + AlON mainly composed of an aluminum element is most preferable for the heat transfer tube of the present invention in terms of performance. This is because, in the present invention, the ceramic alloy composite material is desired to have high temperature corrosion resistance of ceramic properties and ductility of alloy properties, but in this respect, aluminum element is compared with the main element constituting other ceramic alloy composite materials. It is optimal in terms of ductility. The contact surface between the heat-resistant alloy and the ceramic alloy composite material also has the advantage that the rate of breakage during expansion and contraction is less than other ceramic alloy composite materials by using an aluminum-based ceramic alloy composite material with excellent ductility. Yes.
[0029]
The ceramic alloy composite material mainly composed of the aluminum element can be obtained, for example, by press-molding a mixed powder of a low-purity Al source powder and a high-purity Al source powder and sintering the compact. The low-purity Al source powder is, for example, not metal Al or Al alloy powder, and may contain alloy elements such as Si and Mg. The high-purity Al source powder contains, for example, 90 wt% or more of Al. The filler obtained by molding these mixed powders is heated in a nitrogen atmosphere. Al in the powder melts (the melting point of pure Al is 660 ° C., but the melting point of Al—Mg alloy drops to 450 ° C., and the melting point of Al—Si alloy drops to 577 ° C.), 680 When it reaches ° C., a certain amount of Al becomes N in the atmosphere.₂To AIN, and a small amount of unreacted Al is dispersed in AIN. Since AlN having ceramic properties forms a film around Al, the manufactured cover material 3 made of a ceramic alloy composite material of AIN + Al + AlON will not melt and lose its shape even when exposed to a high temperature above the melting point of Al. Absent. In addition, since the degree of nitriding can be controlled by setting the temperature and pressure during molding and heating, the AIN concentration that enhances the ceramic characteristics can be adjusted according to the conditions of the high-temperature exhaust gas and the amount of recovered heat. If the concentration of AIN or Al cannot be set at the time of molding and heating, AIN or Al may be supplied between the ceramic alloy composite material and the heat-resistant alloy.
[0030]
The ceramic alloy composite material mainly composed of an aluminum element may be blended as long as it has a good heat resistance in addition to AlN and Al. That is, TiO₂, ZrO₂, Cr₂O_Three, Al₂O_Three, SiO₂, Y₂O_Three, CeO₂, Sc₂O_ThreeOne or a plurality of oxides selected from the above, and a composite oxide containing at least one of these oxides may also be included. BN, MgB₂, CaB₆, TiB₂, ZrB₂, AlB₂One or more borides selected from among the above may be contained. B_FourC, TiC, ZrC, Cr_ThreeC₂, Al_FourC_Three, One or more carbides selected from SiC may be included. TiN, ZrN, Cr₂N, Si_ThreeN_FourOne or a plurality of nitrides selected from among them may be contained. Si₂N₂An oxynitride represented by O may be contained. Regarding the composition, any composition may be used in the present invention. A part of Al of AlON may be replaced with Si. However, the Si / Al molar ratio is preferably 1.0 or less from the viewpoint of corrosion resistance.
[0031]
  When exposed to high temperatures, the outer surface of the heat-resistant alloy tube 1 and a cover material made of a ceramic alloy composite material3In order to improve the mutual sliding of the inner surface of the heat resistant alloy tube 1, BN or B_FourA compound containing boron or carbon such as C is applied. This functions as a mold release agent that more effectively prevents the adhesion between the ceramic material and the metal and makes each slip better. The applied thickness is preferably 1 to 60 microns.
[0032]
In the high temperature exhaust gas, there are a condensate composed of a gaseous body of HCl and SOx and a basic salt such as NaCl and KC1 as corrosive substances. This condensate has a size of the order of submicron with a small one and about 20 microns with a large one forming an aggregate. In order to keep the heat exchanger tube for heat exchange of the present invention at low cost, it is effective to set the porosity of the ceramic alloy composite material to 2% or more. However, if the porosity is too large, the corrosive condensate However, when the porosity is more than 60%, it is found that the effect of the present invention cannot be exhibited.
[0033]
FIG. 2 shows a side shape and a cross section of a heat transfer tube for heat exchange according to the present invention. The heat transfer heat transfer tube is set in an atmosphere in which a high-temperature gas flows, and the fluid to be heated enters the heat-resistant alloy tube 1 from one end to the other end. Basically, the outer periphery of the heat-resistant alloy tube 1 exposed to the high-temperature gas is covered with a cover material 3 made of a ceramic alloy composite material via a thermal expansion buffer material 2. As described above, the thermal expansion buffer 2 has a non-adhesive structure with respect to the cover material 3 made of the ceramic alloy composite material and / or the heat-resistant alloy tube 1.
[0034]
The flow velocity in the pipe of the fluid to be heated is in accordance with conventional waste combustion or coal combustion boilers, but depending on the purpose, the flow velocity may be changed to a low speed side or a high speed side. The heat-resistant alloy pipe 1 through which the fluid to be heated of the heat transfer pipe for heat exchange flows may have any diameter as long as the fluid to be heated flows, but among them, when the entire circumference of the pipe is exposed to exhaust gas, it should be 15A to 40A Is preferable for manufacturing. The length of the heat exchanger tube for heat exchange is preferably 1 to 6 m. If the heat transfer tube for heat exchange becomes longer, the amount of deflection of the heat-resistant alloy tube 1 increases, and there is a concern about cracking of the ceramic alloy composite material of the cover material 3. The problem can be solved by providing supporting columns and reducing the amount of deflection of the heat-resistant alloy tube 1. Further, as can be seen from FIG. 2, a long heat transfer tube can be made by welding both ends of the heat-resistant alloy tube 1 not covered with the ceramic alloy composite material of the short heat transfer tube.
[0035]
Moreover, another structural example of the heat exchanger tube for heat exchange obtained from the present invention is shown in FIGS. FIG. 3 shows a state where one end of the heat exchange heat transfer tube is closed and the fluid to be heated flows through the heat-resistant tube 4 provided in the heat-resistant alloy tube 1, and the fluid to be heated turns back in the gap between the heat-resistant tube 4 and the heat-resistant alloy tube 1 The portion that is heated to flow and is exposed to a high-temperature gas that heats the fluid to be heated is covered with a cover material 3 made of a ceramic alloy composite material. In the case of this type, the outer diameter of the heat exchanger tube for heat exchange is preferably 30 to 200 mm.
[0036]
FIG. 4 shows a heat exchanger tube for heat exchange in which a heat-resistant alloy tube 1 through which a fluid to be heated flows is formed in a U shape, and an outer portion including the bent portion is covered with a cover material 3 made of a ceramic alloy composite material. The U-shaped bent portion requires more voids 5 because the heat expansion deformation of the heat-resistant alloy and the ceramic alloy composite material is more complicated than the heat transfer tube for heat exchange in the shape of a straight tube.
[0037]
【Example】
(1) In a garbage incineration pilot plant for treating municipal waste and industrial waste, the following several types of heat exchange heat transfer tubes were inserted into a high-temperature exhaust gas at about 950 ° C. to about 650 ° C. from the incinerator.
(1) Heat-resistant alloy tube: SUS304-15A
Thermal expansion buffer material: Layer mainly composed of Al foil components, thickness of 1 to 2 mm
Ceramic alloy composite cover material: Al + AlN + AlON-90wt% or more, wall thickness -4-10mm, porosity 40%
(2) Heat-resistant alloy tube: SUS304-20A
Thermal expansion buffer: Carbon fiber equivalent, thickness 0.2-2mm
Ceramic alloy composite cover material: Al + AlN + AlON-90wt% or more, wall thickness -3-8mm, porosity 20%
(3) Heat-resistant alloy tube: SUS304-20A, outer surface with BN coating
Thermal expansion buffer: Carbon fiber equivalent, thickness 0.2-2mm
Ceramic alloy composite cover material: Al + AlN + AlON-90wt% or more, wall thickness-3-8mm, porosity 20%
(4) Heat-resistant alloy tube: SUS304-20A
Thermal expansion cushioning material: Carbon fiber equivalent, thickness 1-2mm
Ceramic alloy composite cover material: Al₂O_Three-80wt% or more, wall thickness -2-4mm, porosity 30%
N of exhaust gas₂The main component other than is O₂: 2 to 16 (vol, dry)%, HCl: 200 to 600 (vol, dry) ppm, SOx: max 300 (vol, dry) ppm, CO₂: 4 to 19 (vol, dry)%, which is a general exhaust gas atmosphere generated when burning municipal waste and industrial waste.
[0038]
As a result of the exposure test, cracks did not occur in the cover material made of the ceramic alloy composite material under any conditions.
In addition, after the 1200 hour exposure test, each heat transfer tube was taken out and the cross section was observed. It was found that the slip of the cover material was smoother than that of the heat transfer tube (1) (2).
When steam with an inlet temperature of 280 ° C to 400 ° C is used as the fluid to be heated, the possibility of 100ata at 540 ° C or higher is possible at the outlet of the heat transfer tube group for all conditions (1) to (4). I found it.
Moreover, when air or waste combustion exhaust gas was used as the fluid to be heated, it was confirmed that 1000 to 4000 mmAq of air and 50 to 400 mmAq of waste combustion exhaust gas could be heated up to 800 ° C.
However, the cover material made of a ceramic alloy composite material for the heat transfer tube (4) is made of Al having a relatively low thermal conductivity.₂O_ThreeThe heat transfer coefficient was lower than that of heat transfer tubes (1) to (3).
[0039]
(2) City waste is partially oxidized to a reduced exhaust gas atmosphere of about 1000 to 700 ° C.
(5) Heat-resistant alloy tube: Heat-resistant tube for boilers STBA28-20A
Thermal expansion buffer material: Carbon 80wt% or more fiber, thickness 0.5-3mm
Ceramic alloy composite cover material: Al + AIN-86wt%, Al₂O_Three-6wt%, wall thickness -4-5mm, porosity 25%
(6) Heat-resistant alloy pipe: Heat-resistant pipe for boilers STBA28-20A
Thermal expansion buffer material: Carbon 80wt% or more fiber, thickness 1-3mm
Ceramic alloy composite cover material: SiC-95wt% or more, wall thickness -4-5mm, porosity 2%
A heat exchanger tube for heat exchange was inserted.
The fluid to be heated is water vapor and air.
[0040]
As a result of conducting a heat exchange test in a reducing atmosphere with a CO concentration of 5 to 15 (vol, dry)%, the high temperature gas was a reducing gas, so that there was almost no phenomenon in which SiC or AIN was oxidized and deteriorated. A good heat exchange could be carried out.
[0041]
(3) In the combustion exhaust gas of coal, sewage sludge dewatering cake and dry operation sludge incinerator,
(7) Heat-resistant alloy tube: Two types of boiler heat-resistant tubes STBA28-40A and 65A
Thermal expansion support material: Fine powder / fiber mixed layer of carbon 80wt% or more, thickness 0.2-4mm
Ceramic alloy composite cover material: SiC-95wt% or more, wall thickness-approx. 7mm, coaxial tube shape (equivalent to Fig. 3)
(8) Heat-resistant alloy tube: Two types of boiler heat-resistant tubes STBA28-20A and 50A,
Thermal expansion buffer material: Fine powder layer of boron 80wt% or more, thickness 0.3-2mm
Ceramic alloy composite cover material: Al₂O_Three-95 wt% or more, wall thickness-about 4 mm, coaxial tube shape (equivalent to Fig. 3),
(9) Heat-resistant alloy tube: two types of boiler heat-resistant tubes STBA28-15A and 20A,
Thermal expansion buffer: Carbon 80wt% or more fiber, thickness 0.4-1mm
Ceramic alloy composite cover material: Al + AIN-90% or more, wall thickness -6-8mm, U-shape (corresponding to FIG. 4)
A heat exchanger tube for heat exchange was inserted.
[0042]
As a result of the test, the combustion exhaust gas of coal and sewage sludge contains several hundred (vol, dry) ppm of SOx. Even under these conditions, the heat transfer tubes (7) to (9) are not corroded, and the power generation efficiency It has been found that it is possible to recover high temperature and high pressure steam that achieves 30% or more, and also recover high temperature air and high temperature combustion exhaust gas.
[0043]
【The invention's effect】
As described above, the heat exchanger tube for heat exchange according to the present invention is a ceramic alloy composite material having both the properties of ceramics and metal, constituting the excellent toughness of a tube made of a heat-resistant alloy and the cover material covering the outer surface thereof. In addition, a thermal expansion cushioning material is provided between the two members to absorb the difference in thermal expansion, and the thermal expansion cushioning material is provided for the ceramic alloy composite cover material and / or heat resistant alloy tube. The non-adhesive structure prevents damage to the ceramic alloy composite cover material due to thermal shock. As a result, waste combustion exhaust gas, coal combustion exhaust gas, sewage sludge combustion exhaust gas, and other industrial waste This makes it possible to recover high-temperature heat that has been unused so far from the high-temperature corrosive environment in the combustion exhaust gas.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heat exchanger tube for heat exchange according to an embodiment of the present invention.
FIGS. 2A and 2B are a side view and a cross-sectional view of a heat exchanger tube for heat exchange according to the present invention. FIGS.
FIG. 3 is a cross-sectional view showing another embodiment of the present invention.
FIG. 4 is a cross-sectional view showing still another embodiment of the present invention.
[Explanation of symbols]
1 Heat resistant alloy tube
2 Thermal expansion cushioning material
3 Ceramic alloy composite cover material
4 Heat-resistant tube
5 gap

Claims (4)

In a heat exchange tube for heat exchange that is provided in a high temperature gas atmosphere and performs heat exchange from the high temperature gas to a heated fluid in the heat transfer tube,
The pipe through which the fluid to be heated flows is made of a heat-resistant alloy, and the outside of the heat-resistant alloy pipe is covered with a cover material made of a ceramic alloy composite material through a thermal expansion buffer material,
The thermal expansion buffer material has a non-adhesive structure with respect to the cover material and / or the heat-resistant alloy tube made of the ceramic alloy composite material, and the heat-resistant alloy tube and at least a part of the thermal expansion buffer material are in contact with each other, Ri Do a three-layer structure in which at least part of the said thermal expansion buffer member ceramic alloy composite material cover material is in contact,
The ceramic alloy composite material constituting the cover material includes Al and AlN, wherein AlN is 1 wt % or more and 90 wt % or less, and a total ratio of (A1 + AlN + AlON) is 50 wt % or more and 100 wt % or less. Heat exchanger tube for heat exchange.   The thermal expansion cushioning material is made of a material such as a fiber, powder, film, or tape whose main component is boron, carbon, or aluminum, and is used for the outer surface of the heat-resistant alloy tube or the cover material made of the ceramic alloy composite material. The heat exchanger tube for heat exchange according to claim 1, comprising a thermal expansion absorption layer having voids formed on the inner surface. The heat transfer heat transfer tube according to claim 1 or 2 , wherein a release agent made of a compound containing boron or carbon is applied to an outer surface of the heat resistant alloy tube. The heat transfer heat transfer tube according to any one of claims 1 to 3 , wherein the ceramic alloy composite material has a porosity of 2% to 60%.

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